1) 15 minutes? If you flew in a small aircraft regularly, you would know it takes 40-60 minutes to prep a plane from park to airborne in zero traffic.
2) Estimating what the fuel consumption of a small aircraft will be is much, much harder than a surface vehicle. Consider 90% private aviation disasters are a result of pilot error. And 90% of pilot error is in fuel consumption estimation.
15 minutes? If you flew in a small aircraft regularly,
you would know it takes 40-60 minutes to prep a plane
from park to airborne in zero traffic
If there is unavoidable time consuming checking, you could do that in advance and provide the plane as an autonomous taxi. So it shows up, picks you up, drops you off.
Yes, but...
Things like "check your propeller for cracks", or "verify that the control surfaces are actually moving when the controls say they should have moved" should not be skipped.
But you can skip a lot of things just by virtue of this being an electric vehicle - like "visually verify fuel level without using the gauge", or "check oil level", or "test carb heat" or "verify dual magnetos" etc.
It takes 10-15min (max!) to check a Cessna 152, start, and call for departure clearance. Add on another 10-15min for taxi via the pumps & power+pre-take-off checks, you still have 30min left to play with.
I do agree with your main point that you don't just hop in and turn the key, just think that an hour for all that is taking your sweet time.
Also, with a computer flying, you can do something less extreme: actively and continuously manage the compromise between speed and efficiency. If your confidence of reaching your destination drops below the required threshold (say 99.999%), slow to whatever speed is required to achieve that confidence.